1. Field of the Invention
This invention relates to an optical device, and more particularly, to an optical device having a conical field of regard which may be used to view an area with a wide angle of view.
2. Background Information
In many instances it is desirable to use a magnifying optical device having a generally narrow cylindrical field of view, such as a telescope, to view a large area with a large field of regard. Such a device is typically fabricated in a long tube and includes two or more lenses used for magnifying the image being viewed. Viewing a large area is typically accomplished by moving the end of the optical device relative to a stationary eye piece in order to view many small fields, or sub-areas, within the overall larger area to be viewed. By moving the end of the optical device remote from the eyepiece, a large viewing aperture is acquired.
In many instances, there is a difficulty in providing a large viewing aperture. For example, some viewing areas require special materials, such as sophisticated microwave or infrared filters, which are expensive to fabricate, particularly in large areas. Further, space limitations may prevent a large aperture from being available.
3. Description of the Prior Art
The prior art has suggested using a narrow field of view optical device, which is rotated throughout the area to be viewed in order to obtain mapping data regarding the entire area being viewed. For example, see U.S. Pat. No. 4,717,822 in the name of Robert W., Byrens and entitled "Rosette Scanning Surveillance Sensor". The Byrens device utilizes generally orthogonal gimbals and thus is complicated, expensive and is difficult to control. What is needed is a simpler and more effective optical device to permit scanning and mapping of a wide area using a narrow field of view optical device which views through a small aperture.